Opened up System Profiler, and noticed to oddities: 1. The Optical drive uses the (faulty) SATA 3Gbps port, not the (good) SATA 6Gbps port. The hard drive does use the 6 Gbps port, although it is only a 3 Gbps device (the 750 GB drive, at least.) The optical drive is connected to a 3 Gbps port, but only connects at 1.5 Gbps (even the fastest optical drive is slower than that, so the actual link speed doesn't really matter.) 2. The Radeon GPU is only connected via a 8-lane PCI Express connection. The chipset does have a 16-lane connection that is supposed to be for graphics cards, and the switching from onboard to discrete (according to Intel) should be fully possible using the entire 16-lane connection. The only thing I could think of is that Thunderbolt uses the other 8 lanes.